Phospholipids, such as lecithin, are amphipathic compounds in that they consist of both hydrophobic and hydrophilic groups or regions within the same molecule. The balance between these hydrophobic and hydrophilic regions determines their physical properties in an aqueous environment. The uses of natural phospholipids as additives are numerous in the food industry (for example, as emulsifiers), in cosmetics, for industrial uses and for the pharmaceutical industry, especially in the preparation of drug-delivery systems. U.S. Pat. Nos. 4,086,257; 4,097,502; 4,145,410; and 4,159,988 disclose various modifications of the polar-head-group region of natural phospholipids which lead to unique and unexpected physical properties.
Further, various derivatives of lecithin are known, such as, for example, oxyalkylated lecithin compounds (see U.S. Pat. Nos. 3,085,100 and 2,310,679) and phosphatidylalkanolamine derivatives (see, for example, U.S. Pat. Nos. 2,801,255; 3,542,820; 3,577,466; and 4,254,115). It is desirable to provide novel, synthetic phospholipids, particularly having enhanced solubility and surfactant properties in an aqueous environment, especially for the formulation of water-insoluble materials, such as drugs or cosmetic ingredients, within an aqueous environment.
The parent application describes novel, synthetic phospholipid compounds, such as phosphatidylalkanolamine carboxyl polyalkylene glycol like phosphatidylethanolamine carboxyl polyethylene glycol compounds. These novel compounds are prepared by the covalent reaction of a carboxylic analog of the polyalkylene glycol with the phosphatidylalkanolamine, to provide novel, biodegradable, phospholipid compounds which contain an amide linkage.